This research review sought to discover the forms of family verbal interaction that nurture language development in infants and toddlers, the function of different family members in this process, and the role of environmental factors in language development. Results indicate that speech to a child is significantly different from speech to an adult. When speaking to infants and toddlers, adults often use coaction, alternation, prompting, imitation, repetition, and labeling in their interactions. These features tend to change as the child acquires language and may include the expansion of utterances as the child begins to talk. The review also found that not only mothers and fathers, but adults in general, contribute to the language acquisition of children through the use of features that simplify language. Interactions with older siblings may also contribute to language acquisition, but their interactions are less effective than those of adults. The results suggest that infants and toddlers should interact as much as possible with adults to help facilitate the children's language development. (MDM)